Push planning for unserviceable parts to facilitate repair planning in a repair network

ABSTRACT

In one embodiment, a method for repair planning for a location in a repair network includes modeling: (1) an uninspected buffer for parts received but not yet inspected at the location; (2) a first buffer for parts inspected at the location and repairable at the location; (3) a second buffer for parts inspected at the location and not repairable at the location; (4) a third buffer for parts inspected at the location and not repairable at any location in the repair network; and (5) a fourth buffer for parts inspected at the location and serviceable without repair. The parts in the uninspected buffer are assigned to the first, second, third, and fourth buffers at corresponding rates according to an inspection operation. One or more operation plans are generated to push parts out of the uninspected buffer to the first, second, third, and fourth buffers according to the corresponding rates, a part pushed out being available within the first, second, third, or fourth buffer only after a predetermined disposition time has elapsed. An operation plan is generated to push parts out of the second buffer to one or more upstream locations, a part pushed out being available at an upstream location only after a predetermined move lead time has elapsed. For each part pushed out of the uninspected buffer to the first or second buffer, the earliest time at which repair can begin for the part is estimated, this earliest repair time determining the earliest time at which, after the part has been repaired to make it serviceable, the part can be available to satisfy a demand at the location.

RELATED APPLICATIONS

This application is related to U.S. application Ser. No. 10/223,845 filed Aug. 19, 2002, entitled “On-Demand Repair Planning,” and U.S. Application No. 10/224,240 filed Aug. 19, 2002, entitled “Pull Planning for Serviceable Parts to Facilitate On-Demand Repair Planning,” both by Amol B. Adgaonkar, Deepak Rammohan, Pradip Som, and Thomas Burkhardt. U.S. application Ser. No. 10/223,845 and U.S. application Ser. No. 10/224,240 are commonly assigned to the assignee of the present invention. The disclosures of the related patent applications are hereby incorporated by reference for all purposes as if fully set forth herein.

TECHNICAL FIELD OF THE INVENTION

This invention relates generally to service parts planning and more particularly to push planning for unserviceable parts to facilitate repair planning in a repair network.

BACKGROUND OF THE INVENTION

A critical aspect of many supply chains is a network of repair locations that cooperate to receive, diagnose, and repair broken or otherwise unusable parts so that these parts can be returned to service and consumed similar to regular inventory. For example, a typical multi-level repair network may include, within a first level, a number of repair centers at a number of locations that receive, diagnose, and repair unusable parts and may each specialize in repairing a particular type of part. If a repair center is able to repair a part, then the repair center may repair the part and ship the repaired part to one of a number of stocking locations for consumption. If the repair center is unable to repair the part, however, then the part may need to be shipped to one of a number of central repair centers within a second level, which may each specialize in repairing a particular type of part, where the part is again received, diagnosed, and hopefully repaired. If the central repair center is able to repair a part, then the repair center may ship the repaired part to an appropriate stocking location. If the central repair center is unable to repair the part, however, then the part may need to be further shipped to a vendor of the part within a third level, where the part is once again received, diagnosed, and hopefully repaired. If the vendor is able to repair a part, the vendor may ship the repaired part to an appropriate stocking location or warehouse. If the vendor is unable to repair the part, however, the part may simply be discarded.

In certain industries, such repair processes may be very expensive, involving costs associated with temporary storage, diagnosis, and possibly repair of a part at each repair location in the repair network to which the part is shipped. Additional costs are incurred while a part remains unconsumed at a stocking location. Further costs must be incurred to ship a part between repair locations in the repair network. Repair planning involves attempts to minimize undesirable costs associated with broken or otherwise unusable parts to improve the cost-efficiency of the supply chain and increase overall profitability. Previous repair planning techniques have been inadequate in many supply chain environments.

SUMMARY OF THE INVENTION

According to the present invention, disadvantages and problems associated with previous repair planning techniques may be reduced or eliminated.

In one embodiment of the present invention, a method for repair planning for a repair location in a repair network includes modeling: (1) an uninspected buffer for unserviceable parts received at the repair location but not yet inspected at the repair location; (2) a first buffer for unserviceable parts inspected at the repair location and determined to be repairable at the repair location, the unserviceable parts within the uninspected buffer being assigned to the first buffer at a first rate according to an inspection operation at the repair location; (3) a second buffer for unserviceable parts inspected at the repair location and determined not to be repairable at the repair location, the unserviceable parts within the uninspected buffer being assigned to the second buffer at a second rate according to the inspection operation at the repair location; (4) a third buffer for unserviceable parts inspected at the repair location and determined not to be repairable at any repair location in the repair network, the unserviceable parts within the uninspected buffer being assigned to the third buffer at a third rate according to the inspection operation at the repair location; and (5) a fourth buffer for unserviceable parts inspected at the repair location and determined to be serviceable without repair, the unserviceable parts within the uninspected buffer being assigned to the fourth buffer at a fourth rate according to the inspection operation at the repair location. One or more operation plans are generated for the inspection operation to push unserviceable parts out of the uninspected buffer to the first, second, third, and fourth buffers according to the first, second, third, and fourth rates, respectively, the inspection operation having a predetermined disposition time, an unserviceable part that is pushed out of the uninspected buffer being available within the first, second, third, or fourth buffer only after the predetermined disposition time for the inspection operation has elapsed. An operation plan is generated for each of one or more sourcing operations to push unserviceable parts out of the second buffer to one or more upstream repair locations, each upstream repair location being associated with a sourcing operation having a predetermined move lead time, an unserviceable part that is pushed out of the second buffer being available at an upstream repair location only after the predetermined move lead time for the associated sourcing operation has elapsed. For each unserviceable part pushed out of the uninspected buffer to the first or second buffer, the earliest time at which a repair operation can begin for the unserviceable part at the repair location or an upstream repair location is estimated, this earliest repair time determining the earliest time at which, after the unserviceable part has been repaired to make it serviceable, the serviceable part can be available to satisfy a demand at the repair location.

Particular embodiments of the present invention may provide one or more technical advantages. For example, particular embodiments may provide on-demand repair planning, for each of a number of time periods in a planning horizon, based on one or more demands for parts at one or more future times at one or more repair locations. In particular embodiments, a repair location at which the demand exists may be one of multiple repair locations in a multi-level repair network. In particular embodiments, a part may be repaired at a repair location at a latest time that allows the part to be available to help satisfy a demand at a repair location at which the demand exists. In particular embodiments, a part may be moved between repair locations at a latest time that allows the part to be available to help satisfy a demand at a repair location at which the demand exists. In particular embodiments, determining a latest time at which a part can be repaired at a repair location or moved between repair locations may reflect one or more disposition times associated with inspections of the part at one or more repair locations, repair lead times associated with repair of the part at a repair location, one or more move lead times associated with movement of the part between repair locations, and any other appropriate time constraints. In particular embodiments, the present invention allows parts to be repaired (and moved where appropriate) in a “just-in-time” manner, these decisions being made for each of a number of time periods in a planning horizon, each part being repaired (and moved where appropriate) only when needed to satisfy a demand and as late in time as is possible to satisfy the demand. In particular embodiments, the generation of planned repair and move orders may also help integrate planning with execution.

In particular embodiments, the ability to provide on-demand repair planning may minimize undesirable costs associated with broken or otherwise unusable parts, improving the cost-efficiency of the supply chain and increasing overall profitability. For example, in particular embodiments, it may be desirable to repair a part as late in time as possible in order to delay commitment of scarce capital or other resources to the repair process and to make these capital and other resources available for other business activities. As a more particular example, delaying repair may help prevent adding value to a part through repair only to have the repaired part “sit on the shelf” due to a lack of demand. As another more particular example, delaying repair may help minimize losses where the repaired part is likely to suffer attrition due to shelf-life constraints or obsolescence.

Certain embodiments of the present invention may provide all, some, or none of these technical advantages. Certain embodiments may provide one or more other technical advantages, one or more of which may be readily apparent to those skilled in the art from the figures, description, and claims included herein.

BRIEF DESCRIPTION OF THE DRAWINGS

To provide a more complete understanding of the present invention and the features and advantages thereof, reference is made to the following description taken in conjunction with the accompanying drawings, in which:

FIG. 1 illustrates an example service parts planning system;

FIG. 2 illustrates example replenishment planning logic modeled within a replenishment planning system for on-demand repair planning;

FIG. 3 illustrates an example flow of unserviceable parts through a series of repair locations in a repair network;

FIG. 4 illustrates an example push planning phase of a repair planning process;

FIGS. 5A-5F illustrate example buffer profiles; and

FIGS. 6A and 6B illustrate an example pull planning phase of a repair planning process.

DESCRIPTION OF EXAMPLE EMBODIMENTS

FIG. 1 illustrates an example service parts planning system 10. In general, system 10 generates plans relating to supply of service parts to replace broken or otherwise unusable parts. For example, unusable parts may include parts that were unusable at the time the parts were manufactured, parts that became unusable during service, or any other unusable parts.

In one embodiment, system 10 includes a forecasting engine 12 that generates demand forecasts for service parts based on future estimates regarding the number of parts that will break or otherwise become unusable and will need to be replaced. A separate demand forecast may be generated for each of a number of service parts for each of a number of forecasting periods. For example, forecasting engine 12 may generate a new demand forecast for a particular part each month for a specified time period in the future. The time period for a demand forecast is preferably longer than the time to complete the longest expected repair process for the part associated with the demand forecast. For example, in a multi-level repair network including repair centers, central repair centers, vendors, and forward stocking locations, the longest expected repair process may include the sum of: (1) the time to ship the part to the repair center, (2) the time to receive and diagnose a part at a repair center, (3) the time to ship the part from the repair center to a central repair center, (4) the time to receive and diagnose the part at the central repair center, (5) the time to ship the part from the central repair center to the vendor, (6) the time to receive and diagnose the part at the vendor, (7) the time to repair the part at the vendor, and (8) the time to ship the part from the vendor to a central warehouse. For certain parts in certain industries, the horizon corresponding to demand forecasts may therefore need to be several months in length.

System 10 may also include an inventory planning engine 14 that generates inventory plans for service parts, based on demand forecasts obtained from forecasting engine 12, regarding the number of parts that must be maintained in inventory to meet the forecasted demand. A separate inventory plan may be generated for each of a number of service parts for each of a number of planning periods. For example, inventory planning engine 14 may generate a new inventory plan for a particular part each month for a specified time period in the future.

System 10 may also include a replenishment planning engine 16 that generates replenishment plans for service parts, based on demand forecasts obtained from forecasting engine 12, regarding the number of parts that must be repaired through an associated repair network, moved from one location to another location in the repair network, or purchased from a vendor in order to meet the forecasted demand. Replenishment plans are generated for each of a number of service parts throughout the replenishment planning horizon. For example, replenishment planning engine 16 may generate a new replenishment plan for a particular part each day for a specified time period in the future. Each such replenishment plan may specify some combination of repair orders that initiate repair processes, move orders that initiate move processes, and purchase orders that initiate purchase processes. According to the present invention, a replenishment plan may be derived according to on-demand repair planning executed at replenishment planning engine 16. As used herein, the phrase “on-demand” may in particular embodiments be, but need not necessarily be, considered to mean “just-in-time” in the sense that repair orders are planned such that parts are repaired at the latest possible time to satisfy demand.

Particular embodiments of the present invention may provide one or more technical advantages. For example, particular embodiments may provide on-demand repair planning, for each of a number of time periods in a planning horizon, based on one or more demands for parts at one or more future times at one or more repair locations. In particular embodiments, a repair location at which the demand exists may be one of multiple repair locations in a multi-level repair network. In particular embodiments, a part may be repaired at a repair location at a latest time that allows the part to be available to help satisfy a demand at a repair location at which the demand exists. In particular embodiments, a part may be moved between repair locations at a latest time that allows the part to be available to help satisfy a demand at a repair location at which the demand exists. In particular embodiments, determining a latest time at which a part can be repaired at a repair location or moved between repair locations may reflect one or more disposition times associated with inspections of the part at one or more repair locations, repair lead times associated with repair of the part at a repair location, one or more move lead times associated with movement of the part between repair locations, and any other appropriate time constraints. In particular embodiments, the present invention allows parts to be repaired (and moved where appropriate) in a “just-in-time” manner, these decisions being made for each of a number of time periods in a planning horizon, each part being repaired (and moved where appropriate) only when needed to satisfy a demand and as late in time as is possible to satisfy the demand. In particular embodiments, the generation of planned repair and move orders may also help integrate planning with execution.

In particular embodiments, the ability to provide on-demand repair planning may minimize undesirable costs associated with broken or otherwise unusable parts, improving the cost-efficiency of the supply chain and increasing overall profitability. For example, in particular embodiments, it may be desirable to repair a part as late in time as possible in order to delay commitment of scarce capital or other resources to the repair process and to make these capital and other resources available for other business activities. As a more particular example, delaying repair may help prevent adding value to a part through repair only to have the repaired part “sit on the shelf” due to a lack of demand. As another more particular example, delaying repair may help minimize losses where the repaired part is likely to suffer attrition due to shelf-life constraints or obsolescence.

System 10 may include a server system that includes one or more computer systems at one or more locations. Engines 12, 14, 16 may be separate processes each executing on a dedicated processor or may be integrated in whole or in part, for example, all executing on a single processor. Each engine 12, 14, 16 may receive input data from database 18 or otherwise, manipulate the input data and any other suitable data as appropriate, and interact with database 18 as appropriate to provide output data representing demand forecasts, inventory plans, and replenishment plans. Engines 12, 14, 16 may be fully autonomous or may operate at least in part subject to input from users of system 10. Database 18 may provide persistent data storage for system 10 and may store any data suitable to support the operation of system 10. Although the term “database” is used, memory closely associated with one or more engines 12, 14, 16 or another suitable data storage arrangement may be used. Use of the term “database” is meant to encompass all suitable data storage arrangements. In one embodiment, database 18 is populated with data received from one or more data sources internal, external, or both internal and external to the enterprise or facility associated with system 10.

FIG. 2 illustrates example replenishment planning logic 20 modeled within replenishment planning engine 16. Logic 20 may include representations of any suitable number of repair locations 22 within an applicable multi-level repair network. For simplicity, only two repair locations 22 a and 22 b are illustrated. As an example, the first repair location 22 a may be a repair center within a first level in a multi-level repair network, while the second repair location 22 b may be an upstream central repair center within a second level in the multi-level repair network. More generally, repair locations 22 a, 22 b may be any suitable repair locations within the same or different levels of a multi-level repair network.

In one embodiment, a repairable part may have one of two possible states: (1) a serviceable state (meaning that the part is suitable to be put to service), or (2) an unserviceable state (meaning that the part is broken or otherwise unusable and is not suitable to be put to service). In many cases, it is desirable to replenish serviceable parts inventory using parts that are consumed from unserviceable parts inventory after being repaired. Accordingly, in one embodiment, logic 20 includes an Unserviceable buffer 24 and a Serviceable buffer 26 for each repair location 22 within the repair network. Replenishment planning engine 16 may track each part 28 as it moves in accordance with logic 20. Unserviceable parts 28 and serviceable parts 28 may be tracked separately from serviceable parts 28, a suitable transition being made when a part 28 moves from an unserviceable to a serviceable state.

For any buffer within logic 20, a graph of the quantity of parts (i.e. inventory) in the buffer for each of a series of time periods within a planning horizon may be referred to as the buffer profile for the buffer. For example, the time periods may be days such that the buffer profile may indicate the inventory for each day within the planning horizon. Each buffer profile may be constructed according to the inventory produced into the buffer (i.e. incoming inventory) from one or more downstream repair locations 22 at each time period and, similarly, the inventory consumed from the buffer (i.e. outgoing inventory) to one or more upstream repair locations 22 at each time period. It may be desirable to classify inventory already within the buffer at a time period as incoming inventory at the time period. In this case, the inventory in the buffer at any time period is the incoming inventory minus the outgoing inventory, which may be negative under certain circumstances (e.g., if a shipment is approved without any inventory being available). One type of operation plan for an operation may consume from an originating buffer (resulting in an inventory decrease in the associated buffer profile) at a start time of the operation plan and produce into a destination buffer (resulting in an inventory increase in the associated buffer profile) at an end time of the operation plan. Another type of operation plan for an operation may produce into a destination buffer without consuming from an originating buffer, such as in situations where consumption from the originating buffer has already been accounted for.

For purposes of simplicity, operation of logic 20 is described with respect to parts of a particular type, for example, all having the same part number. However, the present invention contemplates logic 20 operating substantially simultaneously with respect to parts of multiple types, for example, having different part numbers. In this case, data associated with parts 28 of a particular type is preferably maintained and processed separately from data associated with parts 28 of other types.

In operation of logic 20, unserviceable parts 28 flow into an Uninspected buffer 30 a of first repair location 22 a. In one embodiment, the buffer profile for an Uninspected buffer 30 may be a determined, for a specified time, according to: (1) incoming inventory including parts 28 within Uninspected buffer 30 (i.e. on hand) at the time, parts 28 in transit or otherwise approved for shipment from one or more downstream repair locations 22 (e.g., reflected in approved move orders) and in an uninspected state at the time, actual demand for parts 28 (e.g., reflected in confirmed repair return requests) at the time, and forecasted demand for parts 28 (e.g., reflected in netted repair return forecasts) at the time; and (2) outgoing inventory including parts 28 approved for inspection at the time. Because parts 28 arrive at first repair location 22 a in an uninspected state, each part 28 in Uninspected buffer 30 a must be inspected according to an Inspection operation and assigned an appropriate condition state. Each Inspection operation may involve one or more received parts 28. In one embodiment, each part 28 may be assigned one of the following condition states: (1) RTS (“Repairable at This Station”), meaning that part 28 is repairable at first repair location 22 a; (2) NRTS (“Not Repairable at This Station”), meaning that part 28 is not repairable at first repair location 22 a; (3) COND (“Condemnable”), meaning that part 28 is not repairable at any repair location 22 and must be discarded; or (4) USE (“Use As Is”), meaning that part 28 was erroneously reported as unserviceable, does not need to be repaired, and may be put to service in its current condition. The RTS, NRTS, COND, and USE terms are used identically throughout the remainder of this document (e.g., USE stands for “Use As Is” in each case). The time required for the Inspection operation may be referred to as the disposition time and may, where appropriate, be represented as a fixed number of days. For example, if incoming inventory arrives at time t=0, then with a one day disposition time that inventory would not be available for any other operation until time t=1.

Where each received part 28 must be assigned one of the four condition states described above, the sum of the rates at which parts 28 are assigned each condition state equals one (i.e. RTS_Rate+NRTS_Rate+COND_Rate+USE_Rate=1.00). In general, a part 28 assigned an NRTS condition state may be sent to any one of a number of other repair locations 22 for repair. Accordingly, a separate NRTS rate may be determined for each other repair location 22 to which parts 28 may be sent and the total NRTS rate for parts 28 may be the sum of the NRTS rates for all other repair locations 22 to which parts 28 may be sent. It may often be desirable to track the rate for each condition state over a specified time period and use the determined rates as default values for repair planning purposes. For example, given a forecasted demand for unserviceable parts 28 and the rate for each condition state for parts 28, a quantity of parts 28 that will be assigned each condition state may be forecasted (e.g., Unserviceable_Demand_Forecast*NRTS_Rate=NRTS_Quantity) for repair planning purposes. In one embodiment, however, where a specified quantity of parts 28 must be repaired or moved between repair locations 22 at a specified time, a confirmed repair or move order, respectively, may be generated to override or increment the RTS rate or NRTS rate, respectively, that would otherwise be used for repair planning purposes.

Where the demand forecasts obtained from forecasting engine 12 represent forecasted returns of unserviceable parts 28, replenishment planning engine 16 may use the forecasted demand directly in its repair planning operations. However, where the demand forecasts obtained from forecasting engine 12 represent forecasted demand for serviceable parts 28, it may not be reasonable in certain cases to equate the received forecasted demand with forecasted demand for unserviceable parts 28. For example, a certain percentage of parts needing replacement may have exploded, may have been lost at the location of failure, or may otherwise be unavailable for repair within the repair network, yet the demand for serviceable replacements for these parts remains present. Accordingly, replenishment planning engine 16 may apply a yield rate to a forecasted demand for serviceable parts 28 obtained from forecasting engine 12 in order to generate a forecasted demand for unserviceable parts 28 that replenishment planning engine 16 may use in its repair planning operations. For example, given a forecasted demand for serviceable parts 28 and a yield rate, a demand for unserviceable parts 28 may be forecasted (e.g., Serviceable_Demand_Forecast*Yield_Rate=Unserviceable_Demand_Forecast).

In one embodiment, logic 20 models the Inspection operation associated with Uninspected buffer 30 a using four sub-operations, one sub-operation for each of the RTS, NRTS, COND, and USE condition states. Based on the Inspection operation, each part 28 may be allocated through a corresponding sub-operation to one of the following buffers: (1) RTS buffer 32 a through an Inspect RTS sub-operation 34 a; (2) NRTS buffer 36 a through an Inspect NRTS sub-operation 38 a; (3) COND buffer 40 a through an Inspect COND sub-operation 42 a; or (4) USE buffer 44 a through an Inspect USE sub-operation 46 a. The disposition times for sub-operations 34 a, 38 a, 42 a, and 46 a are preferably the same, such that a single disposition time is associated with the Inspection operation regardless of which sub-operations 34 a, 38 a, 42 a, and 46 a are performed with respect to particular parts 28.

In one embodiment, the buffer profile for RTS buffer 32 may be a determined for a specified time according to: (1) incoming inventory including parts 28 within RTS buffer 32 (i.e. on hand) at the time and parts 28 that are in transit or otherwise approved for shipment from one or more downstream repair locations 22 (e.g., reflected in approved move orders) and are in a repairable state at the time; and (2) outgoing inventory including parts 28 approved for repair (e.g., reflected in approved repair orders) at the time. The buffer profile for NRTS buffer 36 may be determined for a specified time according to: (1) incoming inventory including parts 28 within NRTS buffer 32 (i.e. on hand) at the time and parts 28 that are in transit or otherwise approved for shipment from one or more downstream repair locations 22 (e.g., reflected in approved move orders) and are in a non-repairable state at the time; and (2) outgoing inventory including parts 28 approved for shipment to one or more upstream repair locations 22 (e.g., reflected in approved move orders) at the time. The inventory reflected in the buffer profile of Unserviceable buffer 24 at a specified time equals the sum of the inventories reflected in the buffer profiles of Uninspected buffer 30, RTS buffer 32, and NRTS buffer 36 at the time.

From NRTS buffer 36 a, parts 28 may be produced into Uninspected buffer 30 b of second repair location 22 b through a suitable Sourcing operation 52 a. In one embodiment, instead of or in addition to being produced into Uninspected buffer 30 b, parts 28 may be consumed from NRTS buffer 36 a and produced into RTS buffer 32 b or NRTS buffer 36 b of second repair location 22 b directly without first passing through Uninspected buffer 30 b. As described above, although second repair location 22 b is illustrated, parts 28 may be consumed from NRTS buffer 36 a and moved to any suitable number of other repair locations 22 through any suitable Sourcing operations 52. Each Sourcing operation 52 may be implemented according to a reverse bill of distribution (BOD) and an associated move order that initiates shipment of unserviceable parts 28 from one repair location 22 to another repair location 22 in the repair network. Since moving a part 28 from one repair location 22 to another repair location 22 through Sourcing operation 52 must take at least some time, a move lead time is associated with each move. The move lead time may differ depending on the originating and terminating repair locations 22. In one embodiment, a move lead time may be represented as a fixed number of days. For example, if parts 28 assigned an NRTS condition state are moved from first repair location 22 a to second repair location 22 b at time t=1, then with a one day move lead time parts 28 would not be available for inspection at second repair location 22 b until time t=2.

From RTS buffer 32 a, parts 28 may be repaired at first location 22 a through a Repair operation 48 a and produced into a Good buffer 50 a for first location 22 a. Since repairing a part 28 must take at least some time, a repair lead time is associated with Repair operation 48. Where appropriate, the repair lead time may be considered the same for all Repair operations 48 and may be represented as a fixed number of days. For example, if parts 28 are repaired at time t=1, then with a one day repair lead time parts 28 would not be available for consumption at Good buffer 50 a until time t=2. From USE buffer 44 a, parts 28 may be produced into Good buffer 50 a through a USE operation 54 a. The lead time associated with USE operation 54 a may equal zero. The inventory reflected in the buffer profile of Serviceable buffer 26 a at a specified time equals the sum of the inventories reflected in the buffer profiles of Good buffer 50 a and USE buffer 44 a at the time.

In one embodiment, Good buffer 50 a may procure serviceable parts 28 on demand from RTS buffer 32 a through Repair operation 48 a, from USE buffer 44 a through USE operation 54 a, or from Good buffer 50 b of second repair location 22 b through an appropriate Sourcing operation 56 a. As described above, although only second repair location 22 b is shown, Good buffer 50 a may procure serviceable parts 28 from any suitable number of other repair locations 22 through any suitable sourcing operations 56. In a more particular embodiment, Good buffer 50 a procures serviceable parts 28 according to a Procure operation 58 a that encompasses Repair operation 48 a, USE operation 54 a, and Sourcing operation 56 a and applies priorities to select a particular buffer 32 a, 44 a, or 50 b from which to consume serviceable parts 28. Serviceable parts 28 are consumed from Serviceable buffer 26 a to be put to service as replacement parts. The buffer profile for Good buffer 50 may be a determined for a specified time according to: (1) “beginning on hand” inventory including parts 28 within Good buffer 50 at the time, parts 28 in transit or otherwise approved for shipment from one or more upstream repair locations 22 or other upstream locations (e.g., reflected in approved move orders) at the time, and parts 28 undergoing or otherwise approved for repair (e.g., reflected in approved repair orders) at the time; and (2) outgoing inventory including parts 28 approved for shipment to one or more downstream repair locations 22 or other downstream locations (e.g., reflected in approved move orders) at the time.

FIG. 3 illustrates an example flow of unserviceable parts 28 through a series of repair locations 22 in a repair network. In this simple example, one hundred unserviceable parts 28 enter the Uninspected buffer 30 a of first repair location 22 a. According to the Inspection operation at first repair location 22 a, twenty parts 28 are assigned an RTS condition state and placed in RTS buffer 32 a according to the RTS rate of 0.2, thirty parts 28 are assigned an NRTS condition state and placed in NRTS buffer 36 a according to the NRTS rate of 0.3, thirty parts 28 are assigned a COND condition state and placed in COND buffer 40 a according to the COND rate of 0.3, and twenty parts 28 are assigned a USE condition state and placed in USE buffer 44 a according to the USE rate of 0.2. The thirty parts 28 in NRTS buffer 36 a of first repair location 22 a are moved through an appropriate Sourcing operation 52 a to the Uninspected buffer 30 b of second repair location 22 b. According to the Inspection operation at second repair location 22 b, fifteen parts 28 are assigned an RTS condition state and placed in RTS buffer 32 b according to the RTS rate of 0.5, twelve parts 28 are assigned an NRTS condition state and placed in NRTS buffer 36 b according to the NRTS rate of 0.4, zero parts 28 are assigned a COND condition state and placed in COND buffer 40 b according to the COND rate of 0.0, and three parts 28 are assigned a USE condition state and placed in USE buffer 44 b according to the USE rate of 0.1. The twelve parts 28 in NRTS buffer 36 b of first repair location 22 a are moved through an appropriate Sourcing operation 52 b to the Uninspected buffer 30 c of third repair location 22 c. According to the Inspection operation at third repair location 22 c, ten parts 28 are assigned an RTS condition state and placed in RTS buffer 32 c according to the RTS rate of 0.8, zero parts 28 are assigned an NRTS condition state and placed in NRTS buffer 36 c according to the NRTS rate of 0.0, two parts 28 are assigned a COND condition state and placed in COND buffer 40 c according to the COND rate of 0.2, and zero parts 28 are assigned a USE condition state and placed in USE buffer 44 c according to the USE rate of 0.0. In one embodiment, replenishment planning engine 16 may implement appropriate rounding logic to ensure that, as in reality, there are integral quantities of parts 28 in each condition state at each repair location 22.

In one embodiment, as discussed above, each Sourcing operation 52 may be implemented according to a reverse BOD and an associated move order according to which unserviceable parts 28 are pushed upstream from one repair location 22 to another repair location 22. As an example and without limitation, using the simple example illustrated in FIG. 3, move orders may be specified as follows:

From From To To Transport Shipment Delivery Loc ID Item ID Loc ID Item ID Mode Date Date Quantity 22a P_Core 22b P_Core REVERSE_BOD 1 2 30 22b P_Core 22c P_Core REVERSE_BOD 3 4 12 Assuming unserviceable parts 28 arrive at the Uninspected buffer 30 a of first repair location 22 a at time t=0, the movement of the thirty NRTS parts 28 into NRTS buffer 36 a through the Inspect NRTS sub-operation 38 a begins after the disposition time associated with the Inspection operation has elapsed. If the disposition time is equal to one time unit, then the movement of the thirty NRTS parts 28 from NRTS buffer 36 a of first repair location 22 a to Uninspected buffer 30 b of second repair location 22 b will begin at time t=1. If the reverse BOD move lead time associated with a first move order from first repair location 22 a to second repair location 22 b is equal to one time unit, then the thirty NRTS parts 28 from first repair location 22 a will arrive at second repair location 22 b at time t=2. The thirty NRTS parts 28 from first repair location 22 a are again subject to the disposition time associated with the Inspection operation at second repair location 22 b. If the disposition time is again equal to one time unit, then the movement of the twelve NRTS parts 28 from NRTS buffer 36 b of second repair location 22 b to Uninspected buffer 30 c of third repair location 22 c will begin at time t=3. If the reverse BOD move lead time associated with a second move order from second repair location 22 b to third repair location 22 b is equal to one time unit, then the twelve NRTS parts 28 from second repair location 22 b will arrive at third repair location 22 c at time t=4.

Referring again to FIG. 2, in one embodiment, replenishment planning engine 16 performs a first push planning phase in which unserviceable parts 28 are first pushed from Uninspected buffer 30 of each repair location 22 to RTS buffer 32, NRTS buffer 36, COND buffer 40, and USE buffer 44 of each repair location 22 and then pushed from NRTS buffer 36 of each repair location 22 to destination buffers of one or more other repair locations 22 in the repair network. In general, in the first push planning phase, for each unserviceable part 28 at each repair location 22, replenishment planning engine 16 may estimate the earliest time at which a Repair operation 48 can begin for part 28 at that or another repair location 22 and thus the earliest time at which, after part 28 has been repaired, serviceable part 28 can be available to be put to service to satisfy demand at that repair location 22. This may allow replenishment planning engine 16 to estimate based on forecasted demand, within a second pull planning phase described more fully below, the latest time at which to repair each part 28 and thus the time at which to generate a repair order for each part 28, enabling on-demand repair planning.

Parts 28 are pushed from Uninspected buffer 30 to RTS buffer 32, NRTS buffer 36, COND buffer 40, and USE buffer 44 according to the corresponding RTS, NRTS, COND, and USE rates. As described above, the disposition time for the Inspection operation must elapse before parts 28 may be placed into buffers 32, 36, 40, 44. Unserviceable parts 28 are then pushed upstream from NRTS buffer 36 to Uninspected buffers 30 (possibly to RTS buffers 32 or NRTS buffers 36 instead of or in addition to Uninspected buffers 30) of one or more other repair locations 22 according to reverse BODs and associated move orders. As described above, the associated move lead time must elapse before parts 28 may be placed into a destination buffer of the other repair location 22. After parts 28 are repaired at another repair location 22, one or more move lead times must elapse before these repaired parts 28 reach the repair location 22 from which these parts 28 entered the repair network and are available to be put to service to satisfy demand at the repair location 22.

FIG. 4 illustrates an example push planning phase of a repair planning process. In a first general step of the first push planning phase, the replenishment planning engine 16 pushes unserviceable parts 28 in Uninspected buffer 30 of each repair location 22 out to RTS buffer 32, NRTS buffer 36, COND buffer 40, and USE buffer 44 of repair location 22. The first general step may be performed periodically in a series of iterations. In a second general step of the first push planning phase, the replenishment planning engine 16 pushes unserviceable parts 28 from NRTS buffers 36 of each repair location 22 to Uninspected buffers 30 (possibly to RTS buffers 32 or NRTS buffers 36 instead of or in addition to Uninspected buffers 30) of one or more upstream repair locations 22 according to corresponding reverse BODs. The second general step may also be performed periodically in a series of iterations. In one embodiment, for a particular planning cycle, all iterations of the first general step are performed before any iterations of the second general step may begin. However, iterations within each step may overlap. For example, replenishment planning engine 16 may perform a second iteration of the first general step that overlaps in whole or in part with a first iteration of the first general step. Example overlap rules for the second general step are described more fully below in connection with step 112.

In one embodiment, to push unserviceable parts 28 in Uninspected buffer 30 of each repair location 22 out to RTS buffer 32, NRTS buffer 36, COND buffer 40, and USE buffer 44 of repair location 22 in the first general step of the first push planning phase, at step 100 replenishment planning engine 16 sorts the Inspection operations that are in-progress at Uninspected buffer 30 of each repair location 22 and generates operation plans for Inspect RTS sub-operation 34, Inspect NRTS sub-operation 38, Inspect COND sub-operation 42, and Inspect USE sub-operation 46 that produce parts 28 into RTS buffer 32, NRTS buffer 36, COND buffer 40, and USE buffer 44, respectively, according to the RTS, NRTS, COND, and USE rates, respectively. In-progress Inspection operations may be sorted according to the time at which the Inspection operations will complete, in-progress Inspection operations completing earlier being placed before in-progress Inspection operations completing later. An Inspection operation may be considered in-progress if it has begun before the current time under consideration and the disposition time will elapse after the current time under consideration. For example, if the current time under consideration is today, an unserviceable part 28 arrived at Uninspected buffer 30 yesterday, and the disposition time is two days, then the Inspection operation with respect to part 28 may be considered in-progress since the Inspection operation will complete tomorrow. Because each Inspection operation is associated with one or more parts 28, sorting Inspection operations in time may be equivalent to sorting parts 28 in time according to when the associated Inspection operations will complete. This sorting is performed such that parts 28 for which the Inspection operation will complete sooner are processed before other parts 28 for which the Inspection operation will complete later. As described above, an operation plan may specify a start time, an end time (i.e. the start time plus the lead time for the operation), a quantity of parts 28 (i.e. determined according to the rate for the operation), a buffer from which parts 28 are being consumed, and a buffer into which parts 28 are being produced. For in-progress Inspection operations, associated parts 28 have already (i.e. before the current time) been consumed from Uninspected buffer 30 for inspection. Thus, these operation plans involve producing parts 28 into the destination buffers after inspection, but not consuming parts 28 from Uninspected buffer 30.

At step 102, replenishment planning engine 16 traverses the buffer profile of Uninspected buffer 30 of each repair location 22, identifying and accounting for each increase and decrease in the buffer profile. As described above, the buffer profile may be a determined for a specified time according to: (1) beginning on hand inventory including parts 28 within Uninspected buffer 30 at the time, parts 28 in transit or otherwise approved for shipment from one or more downstream repair locations 22 (e.g., reflected in approved move orders) and in an uninspected state at the time, actual returns for parts 28 (e.g., reflected in confirmed return requests) at the time, and forecasted demand for parts 28 (e.g., reflected in netted repair return forecasts) at the time; and (2) outgoing inventory including parts 28 approved for inspection at the time.

Parts 28 within Uninspected buffer 30 are in an uninspected state (i.e. the Inspection operation has not yet completed for these parts 28). In one embodiment, steps 104 and 106 are performed for each in-progress Inspection operation based on the sorting performed at step 100, such that steps 104 and 106 for an in-progress Inspection operation may overlap in part with steps 104 and 106 for a subsequent in-progress Inspection operation. At step 104, for each future time for which the buffer profile of Uninspected buffer 30 indicates an inventory increase (i.e. parts 28 produced into Uninspected buffer 30), replenishment planning engine 16 estimates the quantity of parts 28 that can be acceptably pushed out of Uninspected buffer 30 through the Inspection operation to one or more of RTS buffer 32, NRTS buffer 36, and USE buffer 44 and generates corresponding operation plans for Inspect RTS sub-operation 34, Inspect NRTS sub-operation 38, Inspect COND sub-operation 42, and Inspect USE sub-operation 46, respectively, according to the RTS, NRTS, COND, and USE rates, respectively. These operation plans involve both consuming parts 28 from Uninspected buffer 30 and producing parts 28 into the destination buffers after inspection. The quantity of parts 28 that can be acceptably pushed out of Uninspected buffer 30 may be the quantity that can be pushed out without causing a situation in which an approved Inspection operation, for a specified quantity of parts 28 at a specified time in the future, cannot take place because there are insufficient parts 28 within Uninspected buffer 30 for the approved Inspection operation to take place at the specified time in the future. For example, if ten parts 28 arrived at Uninspected buffer 30 at time t=0, then replenishment planning engine 16 will estimate upon traversing the buffer profile at time t=0 that all ten parts 28 can be pushed out of Uninspected buffer 30. However, if a future approved Inspection operation for five parts 28 is scheduled for time t=4, all ten parts 28 are inspected at time t=0, and there is no incoming inventory in the meantime, then the future approved inspection scheduled for time t=4 cannot actually take place. Thus, in this particular example, a maximum of five parts 28 can be pushed out of Uninspected buffer 30 at time t=0.

At step 106, for each future time for which the buffer profile of Uninspected buffer 30 indicates an inventory decrease as a result of an approved Inspection operation (i.e. parts 28 consumed from Uninspected buffer 30), replenishment planning engine 16 generates operation plans, ending at the time specified in the approved inspection, for Inspect RTS sub-operation 34, Inspect NRTS sub-operation 38, Inspect COND sub-operation 42, and Inspect USE sub-operation 46 suitable for pushing parts 28 out of Uninspected buffer 30 to RTS buffer 32, NRTS buffer 36, COND buffer 40, and USE buffer 44, respectively, according to the RTS, NRTS, COND, and USE rates, respectively. Operation plans associated with Uninspected buffers 30 may be generated in any appropriate order. Like the operation plans described above in connection with step 100, these operation plans involve producing parts 28 into the destination buffers after inspection, but not consuming parts 28 from Uninspected buffer 30. In one embodiment, appropriate rounding logic may be applied to ensure that, as in reality, integral quantities of parts 28 are moved to each buffer 32, 36, 40, 44. In a more particular embodiment, a raw operation plan is generated for each sub-operation 34, 38, 42, 46, which may specify a non-integral quantity of parts 28 for sub-operation 34, 38, 42, 46 according to the corresponding rates. Based on application of rounding logic, a final operation plan may then be generated for each sub-operation 34, 38, 42, 46 that specifies an integral quantity of parts 28 for sub-operation 34, 38, 42, 46. At step 108, for each repair location 22, replenishment planning engine 16 pushes appropriate parts 28 out of Uninspected buffer 30 to RTS buffer 32, NRTS buffer 36, COND buffer 40, and USE buffer 44 according to the corresponding operation plans.

At step 110, in one embodiment, replenishment planning engine 16 traverses repair locations 22 in the repair network level by level, starting with the most downstream repair locations 22 and moving upstream. In one example, this involves traversing all downstream repair locations 22 (e.g., at the level of first repair location 22 a in FIG. 3), then traversing all repair locations 22 in the next upstream level (e.g., at the level of second repair location 22 b in FIG. 3), then traversing all repair locations 22 in the next upstream level (e.g., at the level of third repair location 22 c in FIG. 3), and so on. The manner in which repair locations 22 are traversed may, in certain embodiments, depend on one or more other considerations.

In one embodiment, step 112 is performed for each repair location 22 as it is reached during the traversal of step 110. In addition, in one embodiment, steps 112 and 114 are not necessarily performed sequentially, such that steps 112 and 114 may in general overlap according to the buffer profile of NRTS buffer 36. At step 112, for a repair location 22 traversed in step 110, for each future time for which the buffer profile of NRTS buffer 36 indicates an inventory increase (i.e. parts 28 produced into NRTS buffer 36 from Uninspected buffer 30 according to Inspect NRTS sub-operation 38), replenishment planning engine 16 estimates the quantity of parts 28 that can be acceptably pushed out of NRTS buffer 36 through one or more Sourcing operations 52 to one or more upstream repair locations 22 and generates corresponding operation plans for Sourcing operations 52 accordingly. As described above, an operation plan may specify a start time, an end time (i.e. the start time plus the transit time for the move), a quantity of parts 28 being moved (i.e. determined according to the NRTS rate), a repair location 22 from which parts 28 are being moved, and a repair location 22 to which parts 28 are being moved. These operation plans involve both consuming parts 28 from NRTS buffer 36 and producing parts into the destination buffers of upstream repair locations 22. The quantity of parts 28 that can be acceptably pushed out may be the quantity that can be pushed out without causing a situation in which a future approved Move operation cannot take place because there are insufficient parts 28 within NRTS buffer 36 for the approved Move operation at the time the approved Move operation is scheduled to occur. For example, if ten parts 28 arrived at NRTS buffer 36 at time t=1, replenishment planning engine 16 will estimate upon traversing the buffer profile at time t=1 that ten parts 28 can be pushed out of NRTS buffer 36. However, if a future approved Move operation for five parts 28 is scheduled for time t=5, all ten parts 28 are moved out at time t=1, and there is no incoming inventory in the meantime, then the approved move scheduled for time t=5 cannot actually take place. Thus, in this particular example, a maximum of five parts 28 can be pushed out of NRTS buffer 36 at time t=1. Where repair locations 22 in the repair network are traversed level by level as described above, performance of step 112 for a repair location 22 may overlap in whole or in part with performance of step 112 for one or more other repair locations 22 in the same level, but step 112 is performed for all repair locations 22 in a level before step 112 is performed for any repair location 22 in another level upstream of that level.

At step 114, for each future time for which the buffer profile of NRTS buffer 36 indicates an inventory decrease as a result of one or more approved Move orders to one or more upstream repair locations 22 (i.e., parts 28 consumed from NRTS buffer 36), replenishment planning engine 16 generates one or more operation plans for the one or more corresponding Sourcing operations 52, which may involve one or more associated reverse BODs. These operation plans involve producing parts 28 into the destination buffers after Sourcing operation 52 has completed, but not consuming parts 28 from NRTS buffer 36. Where parts 28 may be pushed out of NRTS buffer 36 to multiple upstream repair locations 22 based on the NRTS rates defined on the associated reverse BODs, appropriate rounding logic may be applied to ensure that, as in reality, integral quantities of parts 28 are moved to each such repair location 22. In a more particular embodiment, a raw operation plan is generated for each Sourcing operation 52, which may specify a non-integral quantity of parts 28 for Sourcing operation 52 according to the corresponding NRTS rate. Based on application of rounding logic, a final operation plan may then be generated for each Sourcing operation 52 that specifies an integral quantity of parts 28 for Sourcing operation 52. At step 116, for each repair location 22, replenishment planning engine 16 pushes appropriate parts 28 out of NRTS buffer 36 to Uninspected buffers 30 (possibly to RTS buffers 32 or NRTS buffers 36 instead of or in addition to Uninspected buffers 30) of one or more upstream repair locations 22 according to the corresponding operation plans generated at step 114. Steps 114 and 116 may be performed level by level in the same manner described above with respect to step 112.

Referring again to FIG. 2, in one embodiment, replenishment planning engine 16 performs a second pull planning phase in which replenishment planning engine 16 generates on-demand or just-in-time operation plans for RTS operation 34, USE operation 46, and Sourcing operation 56 at each repair location 22 based on demand forecasts for each repair location 22 obtained from forecasting engine 12. Instead of merely using Sourcing operation 56 to procure serviceable parts 28 to meet forecasted demand at a repair location 22, replenishment planning engine 16 attempts to pull serviceable parts 28 first from USE buffer 44 through USE operation 54 from USE buffer 44 at repair location 22. If the quantity or time of availability of serviceable parts 28 in USE buffer 44 is not sufficient to satisfy forecasted demand, then as a second option replenishment planning engine 16 attempts to pull serviceable parts 28 from RTS buffer 32 through Repair operation 54 at repair location 22. If the quantity or time of availability of serviceable parts 28 in USE buffer 44 or available from RTS buffer 32 through Repair operation 54 is not sufficient to satisfy forecasted demand, then as a third option replenishment planning engine 16 attempts to pull serviceable parts 28 from the Good buffers 50 of one or more other repair locations 22 or other locations through one or more associated Sourcing operations 56. If the quantity or time of availability of serviceable parts 28 available through USE operation 54, Repair operation 48, and one or more Sourcing operations 56 is not sufficient to satisfy forecasted demand at repair location 22, then as a final option replenishment planning engine 16 may need to short the demand or, if one or more upstream vendor locations are defined, initiate procurement of serviceable parts 28 from one or more vendors in a traditional manner.

Although a particular priority sequence is described above with respect to procurement of serviceable parts 28, the present invention contemplates any suitable priority sequence being used. For example, to satisfy forecasted demand at repair location 22 for a first part 28 a for which a second part 28 b may be substituted, it may be desirable in one environment to procure serviceable parts 28 according to the sequence: (1) first parts 28 a at repair location 22 on hand or through USE operation 54; (2) second parts 28 b at repair location 22 on hand or through USE operation 54; (3) first parts 28 a from one or more upstream repair locations 22 through Sourcing operations 56; (4) second parts 28 b from one or more upstream repair locations 22 through Sourcing operations 56; (5) first parts 28 a at repair location 22 through Repair operation 48; (6) second parts 28 b at repair location 22 through Repair operation 48; (7) first parts 28 a from one or more vendors in traditional manner; and (8) second parts 28 b from one or more vendors in traditional manner. As another example, it may be desirable in another environment to instead procure serviceable parts 28 according to the sequence: (1) first parts 28 a at repair location 22 on hand or through USE operation 54; (2) first parts 28 a from one or more upstream repair locations 22 through Sourcing operations 56; (3) first parts 28 a at repair location 22 through Repair operation 48; (4) second parts 28 b at repair location 22 on hand or through USE operation 54; (5) second parts 28 b from one or more upstream repair locations 22 through Sourcing operations 56; (6) second parts 28 b at repair location 22 through Repair operation 48; (7) first parts 28 a from one or more vendors in traditional manner; and (8) second parts 28 b from one or more vendors in traditional manner. As a further example, it may be desirable to attempt to satisfy forecasted demand at repair location 22 through procurement of serviceable parts 28 from USE buffer 44 of an upstream repair location 22 that is more than one level removed from the repair location 22 at which the forecasted demand exists, before attempting to procure serviceable parts 28 through Repair operation 48 at the repair location 22 at which the forecasted demand exists. Replenishment planning engine 16 may consider any appropriate prioritization scheme in generating operation plans in an effort to satisfy forecasted demand at each repair location 22. In one embodiment, a user of system 10 may be able to select or otherwise specify a sourcing sequence for each part 28 for each repair location 22.

Example operation of the second pull planning phase may be described using the simple example of FIG. 3 discussed above. Assume a demand at time t=5 of eighty serviceable parts 28 at first repair location 22 a. Also assume that Uninspected buffer 30 a of first repair location 22 a contains one hundred unserviceable parts 28 at time t=0. Also assume the disposition time for each Inspection operation is one unit of time, the repair lead time associated with Repair operation 48 is one unit of time, and the move lead time for each movement between repair locations 22 (whether a forward BOD or reverse BOD) is also one unit of time. Based on replenishment planning engine 16 pushing unserviceable parts 28 within first repair location 22 a, from first repair location 22 a to second repair location 22 b, within second repair location 22 b, from second repair location 22 a to third repair location 22 c, and within third repair location 22 c described above, the quantities of parts 28 in each condition state at each repair location 22 is as follows:

Location RTS NRTS COND USE 22a 20 30 30 20 22b 15 12 0 3 22c 10 0 2 0 Thus, of the one hundred unserviceable parts 28 received at first repair location 22 a and placed in Uninspected buffer 30 a at time t=0, only the twenty parts 28 in USE buffer 44 a are available to satisfy the demand at first repair location 22 a at time t=1 (after the disposition time associated with the Inspection operation at first repair location 22 a has elapsed). The profile of USE buffer 44 a (i.e. the on-hand inventory of serviceable parts 28 at first repair location 22 a) for this example is illustrated in FIG. 5A. The twenty unserviceable parts 28 in RTS buffer 32 a of first repair location 22 a are available for repair at time t=1 and thus cannot be available to satisfy the demand at first repair location 22 a until time t=2 at the earliest (after the added repair lead time for Repair operation 48 a). The profile of RTS buffer 32 a for this example is illustrated in FIG. 5B.

Analogously, of the thirty unserviceable parts 28 received at second repair location 22 b and placed in Uninspected buffer 30 b at time t=2 (after the added move lead time for the reverse BOD from first repair location 22 a to second repair location 22 b), only the three parts 28 in USE buffer 44 b are available at time t=3 (after the added disposition time for the Inspection operation at second repair location 22 b) and cannot be available to satisfy demand at first repair location 22 a until time t=4 (after the added move lead time for the forward BOD from second repair location 22 b back to first repair location 22 a). The profile of USE buffer 44 b for this example is illustrated in FIG. 5C. The fifteen unserviceable parts 28 in RTS buffer 32 b of second repair location 22 b are available for repair at time t=3 (after the added disposition time for the Inspection operation at second repair location 22 b) and thus cannot be available to satisfy demand at first repair location 22 a until time t=5 at the earliest (after the added repair lead time for Repair operation 48 b and also the added move lead time for the forward BOD from second repair location 22 b back to first repair location 22 a). The profile of RTS buffer 32 b for this example is illustrated in FIG. 5D.

Analogously, of the twelve unserviceable parts 28 received at third repair location 22 c and placed in Uninspected buffer 30 c at time t=4 (after the added move lead time for the reverse BOD from second repair location 22 b to third repair location 22 c), USE buffer 44 c contains zero parts 28 at time t=5 (after the added disposition time for the Inspection operation at third repair location 22 c). The profile of USE buffer 44 c for this example is illustrated in FIG. 5E. The ten unserviceable parts 28 in RTS buffer 32 c of third repair location 22 c are available for repair at time t=5 (after the added disposition time for the Inspection operation at third repair location 22 c) and thus cannot be available to satisfy demand at first repair location 22 a until time t=8 at the earliest (after the added repair lead time for Repair operation 48 c and also the two added move lead times for the forward BODs from third repair location 22 c back to second repair location 22 b and from second repair location 22 b back to first repair location 22 a). The profile of RTS buffer 32 c for this example is as illustrated in FIG. 5F.

In one embodiment, based on the demand at time t=5 of eighty serviceable parts 28 at first repair location 22 a and a goal of waiting as long as possible to repair or move parts 28, replenishment planning engine 16 may partially satisfy the demand as follows:

Balance Repair Repair Fulfillment/ Fulfillment Repair Start End Loc RTS USE Demand Repair Unfulfilled Time Potential Time Time 22a 20 80 20 60 5 22a 20 60 20 40 5 0 4 5 22b 3 40 3 37 4 22b 15 37 15 22 5 0 3 4 22c 0 22 0 22 22c 10 22 0 22

The repair orders in this example are:

Repair From To Loc Start End Order ID Item ID Item ID Id Date Date Quantity 0 P_Core P 22a 4 5 20 1 P_Core P 22b 3 4 15

In planning to satisfy the demand at time t=5 of eighty serviceable parts 28 at first repair location 22 a, replenishment planning engine 16 estimates that there are twenty parts 28 on-hand in USE buffer 44 a beginning at time t=1 and that twenty parts 28 in RTS buffer 32 a can be repaired at any time between time t=1 (the earliest time at which these parts 28 can be repaired to satisfy any demand) and time t=4 (the latest time at which these parts 28 can be repaired to satisfy a demand at time t=5). Thus, a total of forty parts 28 from first repair location 22 a itself can be available to satisfy the demand at time t=5. According to the present invention, replenishment planning engine 16 plans a repair order for the twenty parts 28 in RTS buffer 32 a at time t=4, which is as late as possible in this example.

Considering second repair location 22 b, replenishment planning engine 16 estimates that there is a remaining demand at time t=5 at first repair location 22 a for forty parts 28, that three parts 28 on-hand in USE buffer 44 b can be moved back to first repair location 22 a at any time between time t=3 (the earliest time at which these parts 28 can be moved to satisfy any demand) and time t=4 (the latest time at which these parts 28 can be moved to satisfy a demand at time t=5 at first repair location 22 a), and that fifteen parts 28 in RTS buffer 32 b can be repaired at time t=3 (the earliest time at which these parts 28 can be repaired to satisfy any demand and also the latest time at which these parts 28 can be repaired to satisfy a demand at time t=5 at first repair location 22 a). Thus, a total of eighteen parts 28 from second repair location 22 b can be available to satisfy the demand at time t=5 at first repair location 22 a. According to the present invention, replenishment planning engine 16 plans a repair order for the fifteen parts 28 in RTS buffer 32 b at time t=3 and a move order for the three parts 28 in USE buffer 44 b and the fifteen parts 28 in RTS buffer 32 b (after they have been repaired) at time t=4, both of which are as late as possible in this example.

Finally, considering third repair location 22 c, replenishment planning engine 16 estimates that there is a remaining demand at time t=5 at first repair location 22 a for twenty-two parts 28, that zero parts 28 are on-hand in USE buffer 44 c, and that the ten parts 28 in RTS buffer 32 c cannot be repaired until time t=5 (which is past the latest time t=3 at which these parts 28 could be repaired to satisfy a demand at time t=5 at first repair location 22 a). Thus, zero parts 28 from third repair location 22 b can be available to satisfy the demand at time t=5 at first repair location 22 a. According to the present invention, replenishment planning engine 16 plans no move or repair order for parts 28 at third repair location 22 c in this example. Since only fifty-eight parts 28 can be made available to satisfy the demand at time t=5 at first repair location 22 a for eighty parts 28, replenishment planning engine 16 may short the demand or, if there exists a vendor location defined upstream of first repair location 22 a, plan a purchase order for twenty-two parts 28 to meet the shortfall.

In one embodiment, in addition to planning repair orders and move orders as appropriate to provide on-demand repair planning, replenishment planning engine 16 may automatically approve planned repair orders and planned move orders satisfying predefined constraints. As an example, users of system 10 may be allowed to define one or more constraints applicable to repair orders based on repair lead times, repair costs, and other appropriate factors. Similarly, users of system 10 may be allowed to define one or more constraints applicable to move orders based on move lead times, shipping costs, and other appropriate factors. Replenishment planning engine 16 may then automatically approve all planned repair orders and move orders satisfying the applicable predefined constraints, independent of human interaction. Planned repair orders and move orders not satisfying the applicable predefined constraints could be sorted out on an exception basis for human approval. Such automatic approval may further improve the repair planning process by improving speed and accuracy while reducing time and manpower requirements.

FIGS. 6A and 6B illustrate an example pull planning phase of a repair planning process. In summary, in one embodiment, to satisfy a demand for serviceable parts 28 at repair location 22, replenishment planning engine 16 pulls serviceable parts 28 to Good buffer 50 of repair location 22 from USE buffer 44 of repair location 22, from RTS buffer 32 of repair location 22, from Good buffers 50 of one or more upstream repair locations 22, or using traditional procurement operations. In general, to be available to help satisfy the demand, parts 28 must be in Good buffer 50 of repair location 22 at the time of the demand or earlier, considering all the disposition times, repair lead times, and move lead times that may need to be incurred in doing so. At step 200, replenishment planning engine 16 estimates the quantity of parts 28 available in Good buffer 50 of repair location 22 to help satisfy the demand. If no parts 28 are available at step 202, then replenishment planning engine 16 proceeds to step 206. However, if any parts 28 are available at step 202 and these parts 28 are sufficient to filly satisfy the demand at step 206, then the pull planning phase is complete as to the demand.

If the demand is not fully satisfied at step 204, then at step 206 replenishment planning engine 16 estimates the quantity of parts 28 available in USE buffer 44 of repair location 22 to help satisfy the demand. If no parts 28 are available at step 208, then replenishment planning engine 16 proceeds to step 214. However, if any parts 28 are available at step 208, then at step 210 replenishment planning engine 16 generates an appropriate operation plan for USE operation 54 for these parts 28 at repair location 22. If USE operation 54 has a non-zero lead time, then the operation plan may need to take this into account to ensure that these parts 28 are available to help satisfy the remaining demand. If the demand is fully satisfied at step 212, then the pull planning phase is complete as to the demand. However, if the demand is not satisfied at step 212, then at step 214 replenishment planning engine 16 estimates the quantity of parts 28 available in RTS buffer 32 of repair location 22 to help satisfy the remaining demand. If no parts 28 are available at step 216, then replenishment planning engine 16 proceeds to step 226. However, if any parts 28 are available at step 216, then at step 218 replenishment planning engine 16 preferably estimates the latest time at which Repair operation 48 can begin for these parts 28 at repair location 22 in order to help satisfy the remaining demand. Replenishment planning engine 16 plans a repair order for these parts 28 at the estimated latest time at step 220 and, at step 222, generates an appropriate operation plan for Repair operation 48 at repair location 22.

If the demand is fully satisfied at step 224, then the pull planning phase is complete as to the demand. If the demand is not fully satisfied at step 224 and no upstream repair locations 22 exist from which serviceable parts 28 might be procured to help satisfy the remaining demand at step 226, then replenishment planning engine 16 may proceed to step 268 for procurement of parts 28 in a traditional manner to satisfy the remaining demand. If the remaining demand cannot be satisfied in this manner given lead time constraints, then the demand is shorted. However, if one or more appropriate upstream repair locations 22 exist at step 226, then replenishment planning engine 16 selects an upstream repair location 22 at step 228. At step 230, replenishment planning engine 16 estimates the quantity of parts 28 available in Good buffer 50 of upstream repair location 22 to help satisfy the demand. If no parts 28 are available at step 232, then replenishment planning engine 16 proceeds to step 238. However, if any parts 28 are available at step 232, then replenishment planning engine 16 plans a move order (and any associated forward BOD) for these parts 28 at step 234 and, at step 236, generates an appropriate operation plan for Sourcing operation 56 at upstream repair location 22. The move order may be planned at an estimated latest time at which Sourcing operation 56 can begin for these parts 28 at upstream repair location 22 in order to help satisfy the remaining demand.

If the demand is fully satisfied at step 238, then the pull planning phase is complete as to the demand. However, if the demand is not fully satisfied at step 238, then at step 240 replenishment planning engine 16 estimates the quantity of parts 28 available in USE buffer 44 of upstream repair location 22 to help satisfy the remaining demand. If no parts 28 are available at step 242, then replenishment planning engine 16 proceeds to step 268. However, if any parts 28 are available at step 242, then at step 244 replenishment planning engine 16 preferably estimates the latest time at which USE operation 54 can begin for these parts 28 at upstream repair location 22 in order to help satisfy the remaining demand. If USE operation 54 has a non-zero lead time, then the latest time estimate may need to take this into account. Replenishment planning engine 16 plans a move order (and any associated forward BOD) for these parts 28 at the estimated latest time plus any non-zero lead time for USE operation 54 at step 246 and, at step 248, generates appropriate operation plans for USE operation 54 and Sourcing operation 56 at upstream repair location 22.

If the demand is fully satisfied at step 250, then the pull planning phase is complete as to the demand. However, if the demand is not fully satisfied at step 250, then at step 252 replenishment planning engine 16 estimates the quantity of parts 28 available in RTS buffer 32 of upstream repair location 22 to help satisfy the remaining demand. If no parts 28 are available at step 254, then replenishment planning engine 16 proceeds to step 266. However, if any parts 28 are available at step 254, then at step 256 replenishment planning engine 16 preferably estimates the latest time at which Repair operation 48 can begin for these parts 28 at upstream repair location 22 in order to help satisfy the remaining demand. Replenishment planning engine 16 plans a repair order for these parts 28 at the estimated latest time at step 258, plans a corresponding move order (and any associated forward BOD) at the estimated latest time plus the repair lead time for these parts 28 at step 258 and, at step 262, generates appropriate operation plans for Repair operation 48 and Sourcing operation 56 at upstream repair location 22.

If the demand is fully satisfied at step 264, then the pull planning phase is complete as to the demand. However, if the demand is not fully satisfied at step 264, and one or more other appropriate upstream repair locations 22 exist at step 266, then replenishment planning engine 16 returns to step 228 for selection of an appropriate upstream repair location 22 and the pull planning phase proceeds as to the selected upstream repair location 22 in the manner described above. The pull planning phase may continue analogously until no appropriate upstream repair locations 22 exist at step 266, in which case replenishment planning engine 16 may attempt to procure parts 28 from a vendor in a traditional manner to satisfy the remaining demand at step 268. If the remaining demand cannot be satisfied in this manner given lead time constraints, the demand is shorted.

Although the present invention has been described with several embodiments, a plethora of changes, substitutions, variations, alterations, and modifications may be suggested to one skilled in the art, and it is intended that the invention encompass all such changes, substitutions, variations, alterations, and modifications as fall within the spirit and scope of the appended claims. 

1. A system for repair planning for a repair location in a repair network, comprising multiple components collectively operable to: model an uninspected buffer for unserviceable parts received at the repair location but not yet inspected at the repair location; model a first buffer for unserviceable parts inspected at the repair location and determined to be repairable at the repair location, the unserviceable parts within the uninspected buffer being assigned to the first buffer at a first rate according to an inspection operation at the repair location; model a second buffer for unserviceable parts inspected at the repair location and determined not to be repairable at the repair location, the unserviceable parts within the uninspected buffer being assigned to the second buffer at a second rate according to the inspection operation at the repair location; model a third buffer for unserviceable parts inspected at the repair location and determined not to be repairable at any repair location in the repair network, the unserviceable parts within the uninspected buffer being assigned to the third buffer at a third rate according to the inspection operation at the repair location; model a fourth buffer for unserviceable parts inspected at the repair location and determined to be serviceable without repair, the unserviceable parts within the uninspected buffer being assigned to the fourth buffer at a fourth rate according to the inspection operation at the repair location; generate one or more operation plans for the inspection operation to push unserviceable parts out of the uninspected buffer to the first, second, third, and fourth buffers according to the first, second, third, and fourth rates, respectively, the inspection operation having a predetermined disposition time, an unserviceable part that is pushed out of the uninspected buffer being available within the first, second, third, or fourth buffer only after the predetermined disposition time for the inspection operation has elapsed; generate an operation plan for each of one or more sourcing operations to push unserviceable parts out of the second buffer to one or more upstream repair locations, each upstream repair location being associated with a sourcing operation having a predetermined move lead time, an unserviceable part that is pushed out of the second buffer being available at an upstream repair location only after the predetermined move lead time for the associated sourcing operation has elapsed; and for each unserviceable part pushed out of the uninspected buffer to the first or second buffer, estimate the earliest time at which a repair operation can begin for the unserviceable part at the repair location or an upstream repair location, this earliest repair time determining the earliest time at which, after the unserviceable part has been repaired to make it serviceable, the serviceable part can be available to satisfy a demand at the repair location.
 2. The system of claim 1, wherein: the repair network comprises a multi-level repair network, each level in the repair network comprising one or more repair locations at which unserviceable parts may be repaired; and the one or more components are collectively operable to, for each repair location in the repair network: model the uninspected, first, second, third, and fourth buffers; generate one or more operation plans for the inspection operation; generate an operation plan for each sourcing operation; and for each unserviceable part pushed out of the uninspected buffer to the first or second buffer, estimate the earliest repair time.
 3. The system of claim 1, wherein the modeling, generating, generating, and estimating are performed for each of a plurality of times within a planning horizon.
 4. The system of claim 1, wherein the inspection operation encompasses an inspection sub-operation for each of the first, second, third, and fourth buffers, each inspection sub-operation having a predetermined disposition time.
 5. The system of claim 4, wherein the disposition time for each inspection sub-operation comprises one or more full days.
 6. The system of claim 1, wherein each of the first, second, third, and fourth rates is determined according to historical data reflecting actual inspections performed on actual unserviceable parts at the repair location.
 7. The system of claim 1, wherein the second rate comprises a sub-rate for each upstream repair location to which unserviceable parts may be pushed from the second buffer, the second rate equaling the sum of the sub-rates for all upstream repair locations to which unserviceable parts may be pushed from the second buffer.
 8. The system of claim 1, wherein the one or more components are collectively operable to access a forecasted demand for unserviceable parts at the repair location to estimate: a quantity of unserviceable parts that will be received at the repair location for placement in the uninspected buffer; and based on application of the first, second, third, and fourth rates to the received quantity, quantities of unserviceable parts that will be pushed out of the uninspected buffer to the first, second, third, and fourth buffers, respectively.
 9. The system of claim 8, wherein the one or more components are collectively operable to: access a forecasted demand for serviceable parts at the repair location; and apply a yield rate to the forecasted demand for serviceable parts at the repair location to estimate forecasted returns of unserviceable parts at the repair location.
 10. The system of claim 1, wherein the one or more components are collectively operable to: override or increment the first rate according to one or more confirmed repair orders, each confirmed repair order specifying a quantity of unserviceable parts to be pushed out of the uninspected buffer to the first buffer at a specified time; and override or increment the second rate according to one or more confirmed move orders, each confirmed move order specifying a quantity of unserviceable parts to be pushed out of the uninspected buffer to the second buffer at a specified time.
 11. The system of claim 1, wherein generating one or more operation plans for the inspection operation comprises: sorting unserviceable parts in the uninspected buffer for which the inspection operation is in-progress according to the time at which the inspection operation will complete with respect to these unserviceable parts, unserviceable parts for which the inspection operation will complete earlier being ordered before unserviceable parts for which the inspection operation will complete later; generating one or more operation plans for the inspection operation to produce unserviceable parts into the first, second, third, and fourth buffers according to the first, second, third, and fourth rates, respectively; traversing a buffer profile of the uninspected buffer to identify and account for each inventory increase and decrease reflected in the buffer profile; for each future time for which the buffer profile of the uninspected buffer indicates an inventory increase: estimating a quantity of unserviceable parts that can be pushed out of the uninspected buffer to one or more of the first, second, third, and fourth buffers without leaving an insufficient quantity of unserviceable parts in the uninspected buffer for an inspection operation already approved for a specified quantity of unserviceable parts at a specified future time to occur; and generating one or more operation plans for the inspection operation to consume unserviceable parts from the uninspected buffer and produce unserviceable parts into the first, second, third, and fourth buffers according to the first, second, third, and fourth rates, respectively; and for each future time for which the buffer profile of the uninspected buffer indicates an inventory decrease as a result of an inspection operation already approved for a specified quantity of unserviceable parts at a specified future time, generating one or more operation plans for the inspection operation to produce unserviceable parts into the first, second, third, and fourth buffers according to the first, second, third, and fourth rates, respectively.
 12. The system of claim 1, wherein generating one or more operation plans for the inspection operation comprises: generating one or more raw operation plans for the inspection operation, the one or more raw operation plans specifying quantities of unserviceable parts to be pushed out of the uninspected buffer to the first, second, third, and fourth buffers, a raw operation plan possibly specifying a non-integral quantity of unserviceable parts to be pushed out of the uninspected buffer to one or more of the first, second, third, and fourth buffers based on application of the first, second, third, and fourth rates, respectively, to an estimated quantity of unserviceable parts within the uninspected buffer; applying rounding logic to the quantities of unserviceable parts to be pushed out of the uninspected buffer to the first, second, third, and fourth buffers according to the one or more raw operation plans; and according to application of the rounding logic, generating one or more final operation plans for the inspection operation specifying only integral quantities of unserviceable parts to be pushed out of the uninspected buffer to the first, second, third, and fourth buffers.
 13. The system of claim 1, wherein the operation plan for each sourcing operation reflects a move order for initiating shipment of one or more unserviceable parts from the repair location to the associated upstream repair location.
 14. The system of claim 13, wherein the move order specifies a reverse Bill of Distribution (BOD).
 15. The system of claim 1, wherein the move lead time for each sourcing operation comprises one or more full days.
 16. The system of claim 1, wherein generating an operation plan for each of one or more sourcing operations comprises: traversing the repair locations in the repair network level by level, starting with one or more repair locations within a most downstream level and traversing upstream; for each repair location, for each future time for which a buffer profile of the second buffer indicates an inventory increase: estimating a quantity of unserviceable parts that can be pushed out of the second buffer to each of one or more upstream repair locations without leaving an insufficient quantity of unserviceable parts in the second buffer for a move operation already approved for a specified quantity of unserviceable parts at a specified future time to occur; and generating an operation for each sourcing operation according to the estimated quantity to consume unserviceable parts from the second buffer and produce unserviceable parts into one or more destination buffers at the associated upstream repair location; and for each time for which the buffer profile of the second buffer indicates an inventory decrease as a result of a move operation already approved for a specified quantity of unserviceable parts at a specified future time, generating an operation plan for each sourcing operation to produce unserviceable parts into one or more destination buffers at the associated upstream repair location.
 17. The system of claim 1, wherein generating an operation plan for each of one or more sourcing operations comprises: generating a raw operation plan for each sourcing operation, the raw operation plan possibly specifying a non-integral quantity of unserviceable parts to be pushed out of the second buffer to the associated upstream repair location; applying rounding logic to the quantities of unserviceable parts to be pushed out of the second buffer according to the raw operation plans; and according to application of the rounding logic, generating a final operation plan for each sourcing operation specifying an integral quantity of unserviceable parts to be pushed out of the second buffer to the associated upstream repair location.
 18. The system of claim 1, wherein the one or more components are collectively operable to: model for the repair location: an unserviceable parts buffer for unserviceable parts encompassing the uninspected buffer, the first buffer, and the second buffer; and a serviceable parts buffer for serviceable parts encompassing the fourth buffer and a good parts buffer for serviceable parts available to be put to service to help satisfy a demand; and track time-varying inventories of unserviceable parts in the unserviceable parts buffer and serviceable parts in the serviceable parts buffer, the unserviceable parts inventory being tracked separately from the serviceable parts inventory.
 19. The system of claim 1, wherein the system comprises a replenishment planning engine of a service parts planning system.
 20. A method for repair planning for a repair location in a repair network, comprising: modeling an uninspected buffer for unserviceable parts received at the repair location but not yet inspected at the repair location; modeling a first buffer for unserviceable parts inspected at the repair location and determined to be repairable at the repair location, the unserviceable parts within the uninspected buffer being assigned to the first buffer at a first rate according to an inspection operation at the repair location; modeling a second buffer for unserviceable parts inspected at the repair location and determined not to be repairable at the repair location, the unserviceable parts within the uninspected buffer being assigned to the second buffer at a second rate according to the inspection operation at the repair location; modeling a third buffer for unserviceable parts inspected at the repair location and determined not to be repairable at any repair location in the repair network, the unserviceable parts within the uninspected buffer being assigned to the third buffer at a third rate according to the inspection operation at the repair location; modeling a fourth buffer for unserviceable parts inspected at the repair location and determined to be serviceable without repair, the unserviceable parts within the uninspected buffer being assigned to the fourth buffer at a fourth rate according to the inspection operation at the repair location; generating one or more operation plans for the inspection operation to push unserviceable parts out of the uninspected buffer to the first, second, third, and fourth buffers according to the first, second, third, and fourth rates, respectively, the inspection operation having a predetermined disposition time, an unserviceable part that is pushed out of the uninspected buffer being available within the first, second, third, or fourth buffer only after the predetermined disposition time for the inspection operation has elapsed; generating an operation plan for each of one or more sourcing operations to push unserviceable parts out of the second buffer to one or more upstream repair locations, each upstream repair location being associated with a sourcing operation having a predetermined move lead time, an unserviceable part that is pushed out of the second buffer being available at an upstream repair location only after the predetermined move lead time for the associated sourcing operation has elapsed; and for each unserviceable part pushed out of the uninspected buffer to the first or second buffer, estimating the earliest time at which a repair operation can begin for the unserviceable part at the repair location or an upstream repair location, this earliest repair time determining the earliest time at which, after the unserviceable part has been repaired to make it serviceable, the serviceable part can be available to satisfy a demand at the repair location.
 21. The method of claim 20, wherein: the repair network comprises a multi-level repair network, each level in the repair network comprising one or more repair locations at which unserviceable parts may be repaired; and the method further comprises, for each repair location in the repair network: modeling the uninspected, first, second, third, and fourth buffers; generating one or more operation plans for the inspection operation; generating an operation plan for each sourcing operation; and for each unserviceable part pushed out of the uninspected buffer to the first or second buffer, estimating the earliest repair time.
 22. The method of claim 20, wherein the modeling, generating, generating, and estimating are performed for each of a plurality of times within a planning horizon.
 23. The method of claim 20, wherein the inspection operation encompasses an inspection sub-operation for each of the first, second, third, and fourth buffers, each inspection sub-operation having a predetermined disposition time.
 24. The method of claim 23, wherein the disposition time for each inspection sub-operation comprises one or more full days.
 25. The method of claim 20, wherein each of the first, second, third, and fourth rates is determined according to historical data reflecting actual inspections performed on actual unserviceable parts at the repair location.
 26. The method of claim 20, wherein the second rate comprises a sub-rate for each upstream repair location to which unserviceable parts may be pushed from the second buffer, the second rate equaling the sum of the sub-rates for all upstream repair locations to which unserviceable parts may be pushed from the second buffer.
 27. The method of claim 20, further comprising accessing a forecasted demand for unserviceable parts at the repair location to estimate: a quantity of unserviceable parts that will be received at the repair location for placement in the uninspected buffer; and based on application of the first, second, third, and fourth rates to the received quantity, quantities of unserviceable parts that will be pushed out of the uninspected buffer to the first, second, third, and fourth buffers, respectively.
 28. The method of claim 27, further comprising: accessing a forecasted demand for serviceable parts at the repair location; and applying a yield rate to the forecasted demand for serviceable parts at the repair location to estimate forecasted returns of unserviceable parts at the repair location.
 29. The method of claim 20, further comprising: overriding or incrementing the first rate according to one or more confirmed repair orders, each confirmed repair order specifying a quantity of unserviceable parts to be pushed out of the uninspected buffer to the first buffer at a specified time; and overriding or incrementing the second rate according to one or more confirmed move orders, each confirmed move order specifying a quantity of unserviceable parts to be pushed out of the uninspected buffer to the second buffer at a specified time.
 30. The method of claim 20, wherein generating one or more operation plans for the inspection operation comprises: sorting unserviceable parts in the uninspected buffer for which the inspection operation is in-progress according to the time at which the inspection operation will complete with respect to these unserviceable parts, unserviceable parts for which the inspection operation will complete earlier being ordered before unserviceable parts for which the inspection operation will complete later; generating one or more operation plans for the inspection operation to produce unserviceable parts into the first, second, third, and fourth buffers according to the first, second, third, and fourth rates, respectively; traversing a buffer profile of the uninspected buffer to identify and account for each inventory increase and decrease reflected in the buffer profile; for each future time for which the buffer profile of the uninspected buffer indicates an inventory increase: estimating a quantity of unserviceable parts that can be pushed out of the uninspected buffer to one or more of the first, second, third, and fourth buffers without leaving an insufficient quantity of unserviceable parts in the uninspected buffer for an inspection operation already approved for a specified quantity of unserviceable parts at a specified future time to occur; and generating one or more operation plans for the inspection operation to consume unserviceable parts from the uninspected buffer and produce unserviceable parts into the first, second, third, and fourth buffers according to the first, second, third, and fourth rates, respectively; and for each future time for which the buffer profile of the uninspected buffer indicates an inventory decrease as a result of an inspection operation already approved for a specified quantity of unserviceable parts at a specified future time, generating one or more operation plans for the inspection operation to produce unserviceable parts into the first, second, third, and fourth buffers according to the first, second, third, and fourth rates, respectively.
 31. The method of claim 20, wherein generating one or more operation plans for the inspection operation comprises: generating one or more raw operation plans for the inspection operation, the one or more raw operation plans specifying quantities of unserviceable parts to be pushed out of the uninspected buffer to the first, second, third, and fourth buffers, a raw operation plan possibly specifying a non-integral quantity of unserviceable parts to be pushed out of the uninspected buffer to one or more of the first, second, third, and fourth buffers based on application of the first, second, third, and fourth rates, respectively, to an estimated quantity of unserviceable parts within the uninspected buffer; applying rounding logic to the quantities of unserviceable parts to be pushed out of the uninspected buffer to the first, second, third, and fourth buffers according to the one or more raw operation plans; and according to application of the rounding logic, generating one or more final operation plans for the inspection operation specifying only integral quantities of unserviceable parts to be pushed out of the uninspected buffer to the first, second, third, and fourth buffers.
 32. The method of claim 20, wherein the operation plan for each sourcing operation reflects a move order for initiating shipment of one or more unserviceable parts from the repair location to the associated upstream repair location.
 33. The method of claim 32, wherein the move order specifies a reverse Bill of Distribution (BOD).
 34. The method of claim 20, wherein the move lead time for each sourcing operation comprises one or more full days.
 35. The method of claim 20, wherein generating an operation plan for each of one or more sourcing operations comprises: traversing the repair locations in the repair network level by level, starting with one or more repair locations within a most downstream level and traversing upstream; for each repair location, for each future time for which a buffer profile of the second buffer indicates an inventory increase: estimating a quantity of unserviceable parts that can be pushed out of the second buffer to each of one or more upstream repair locations without leaving an insufficient quantity of unserviceable parts in the second buffer for a move operation already approved for a specified quantity of unserviceable parts at a specified future time to occur; and generating an operation for each sourcing operation according to the estimated quantity to consume unserviceable parts from the second buffer and produce unserviceable parts into one or more destination buffers at the associated upstream repair location; and for each time for which the buffer profile of the second buffer indicates an inventory decrease as a result of a move operation already approved for a specified quantity of unserviceable parts at a specified future time, generating an operation plan for each sourcing operation to produce unserviceable parts into one or more destination buffers at the associated upstream repair location.
 36. The method of claim 20, wherein generating an operation plan for each of one or more sourcing operations comprises: generating a raw operation plan for each sourcing operation, the raw operation plan possibly specifying a non-integral quantity of unserviceable parts to be pushed out of the second buffer to the associated upstream repair location; applying rounding logic to the quantities of unserviceable parts to be pushed out of the second buffer according to the raw operation plans; and according to application of the rounding logic, generating a final operation plan for each sourcing operation specifying an integral quantity of unserviceable parts to be pushed out of the second buffer to the associated upstream repair location.
 37. The method of claim 20, further comprising: modeling for the repair location: an unserviceable parts buffer for unserviceable parts encompassing the uninspected buffer, the first buffer, and the second buffer; and a serviceable parts buffer for serviceable parts encompassing the fourth buffer and a good parts buffer for serviceable parts available to be put to service to help satisfy a demand; and tracking time-varying inventories of unserviceable parts in the unserviceable parts buffer and serviceable parts in the serviceable parts buffer, the unserviceable parts inventory being tracked separately from the serviceable parts inventory.
 38. The method of claim 20, wherein the method is performed using a replenishment planning engine of a service parts planning system.
 39. Software for repair planning for a repair location in a repair network, the software embodied in a computer-readable medium and when executed operable to: model an uninspected buffer for unserviceable parts received at the repair location but not yet inspected at the repair location; model a first buffer for unserviceable parts inspected at the repair location and determined to be repairable at the repair location, the unserviceable parts within the uninspected buffer being assigned to the first buffer at a first rate according to an inspection operation at the repair location; model a second buffer for unserviceable parts inspected at the repair location and determined not to be repairable at the repair location, the unserviceable parts within the uninspected buffer being assigned to the second buffer at a second rate according to the inspection operation at the repair location; model a third buffer for unserviceable parts inspected at the repair location and determined not to be repairable at any repair location in the repair network, the unserviceable parts within the uninspected buffer being assigned to the third buffer at a third rate according to the inspection operation at the repair location; model a fourth buffer for unserviceable parts inspected at the repair location and determined to be serviceable without repair, the unserviceable parts within the uninspected buffer being assigned to the fourth buffer at a fourth rate according to the inspection operation at the repair location; generate one or more operation plans for the inspection operation to push unserviceable parts out of the uninspected buffer to the first, second, third, and fourth buffers according to the first, second, third, and fourth rates, respectively, the inspection operation having a predetermined disposition time, an unserviceable part that is pushed out of the uninspected buffer being available within the first, second, third, or fourth buffer only after the predetermined disposition time for the inspection operation has elapsed; generate an operation plan for each of one or more sourcing operations to push unserviceable parts out of the second buffer to one or more upstream repair locations, each upstream repair location being associated with a sourcing operation having a predetermined move lead time, an unserviceable part that is pushed out of the second buffer being available at an upstream repair location only after the predetermined move lead time for the associated sourcing operation has elapsed; and for each unserviceable part pushed out of the uninspected buffer to the first or second buffer, estimate the earliest time at which a repair operation can begin for the unserviceable part at the repair location or an upstream repair location, this earliest repair time determining the earliest time at which, after the unserviceable part has been repaired to make it serviceable, the serviceable part can be available to satisfy a demand at the repair location.
 40. The software of claim 39, wherein: the repair network comprises a multi-level repair network, each level in the repair network comprising one or more repair locations at which unserviceable parts may be repaired; and the one or more components are collectively operable to, for each repair location in the repair network: model the uninspected, first, second, third, and fourth buffers; generate one or more operation plans for the inspection operation; generate an operation plan for each sourcing operation; and for each unserviceable part pushed out of the uninspected buffer to the first or second buffer, estimate the earliest repair time.
 41. The software of claim 39, wherein the modeling, generating, generating, and estimating are performed for each of a plurality of times within a planning horizon.
 42. The software of claim 39, wherein the inspection operation encompasses an inspection sub-operation for each of the first, second, third, and fourth buffers, each inspection sub-operation having a predetermined disposition time.
 43. The software of claim 42, wherein the disposition time for each inspection sub-operation comprises one or more full days.
 44. The software of claim 39, wherein each of the first, second, third, and fourth rates is determined according to historical data reflecting actual inspections performed on actual unserviceable parts at the repair location.
 45. The software of claim 39, wherein the second rate comprises a sub-rate for each upstream repair location to which unserviceable parts may be pushed from the second buffer, the second rate equaling the sum of the sub-rates for all upstream repair locations to which unserviceable parts may be pushed from the second buffer.
 46. The software of claim 39, operable to access a forecasted demand for unserviceable parts at the repair location to estimate: a quantity of unserviceable parts that will be received at the repair location for placement in the uninspected buffer; and based on application of the first, second, third, and fourth rates to the received quantity, quantities of unserviceable parts that will be pushed out of the uninspected buffer to the first, second, third, and fourth buffers, respectively.
 47. The software of claim 46, operable to: access a forecasted demand for serviceable parts at the repair location; and apply a yield rate to the forecasted demand for serviceable parts at the repair location to estimate forecasted returns of unserviceable parts at the repair location.
 48. The software of claim 39, operable to: override or increment the first rate according to one or more confirmed repair orders, each confirmed repair order specifying a quantity of unserviceable parts to be pushed out of the uninspected buffer to the first buffer at a specified time; and override or increment the second rate according to one or more confirmed move orders, each confirmed move order specifying a quantity of unserviceable parts to be pushed out of the uninspected buffer to the second buffer at a specified time.
 49. The software of claim 39, wherein generating one or more operation plans for the inspection operation comprises: sorting unserviceable parts in the uninspected buffer for which the inspection operation is in-progress according to the time at which the inspection operation will complete with respect to these unserviceable parts, unserviceable parts for which the inspection operation will complete earlier being ordered before unserviceable parts for which the inspection operation will complete later; generating one or more operation plans for the inspection operation to produce unserviceable parts into the first, second, third, and fourth buffers according to the first, second, third, and fourth rates, respectively; traversing a buffer profile of the uninspected buffer to identify and account for each inventory increase and decrease reflected in the buffer profile; for each future time for which the buffer profile of the uninspected buffer indicates an inventory increase: estimating a quantity of unserviceable parts that can be pushed out of the uninspected buffer to one or more of the first, second, third, and fourth buffers without leaving an insufficient quantity of unserviceable parts in the uninspected buffer for an inspection operation already approved for a specified quantity of unserviceable parts at a specified future time to occur; and generating one or more operation plans for the inspection operation to consume unserviceable parts from the uninspected buffer and produce unserviceable parts into the first, second, third, and fourth buffers according to the first, second, third, and fourth rates, respectively; and for each future time for which the buffer profile of the uninspected buffer indicates an inventory decrease as a result of an inspection operation already approved for a specified quantity of unserviceable parts at a specified future time, generating one or more operation plans for the inspection operation to produce unserviceable parts into the first, second, third, and fourth buffers according to the first, second, third, and fourth rates, respectively.
 50. The software of claim 39, wherein generating one or more operation plans for the inspection operation comprises: generating one or more raw operation plans for the inspection operation, the one or more raw operation plans specifying quantities of unserviceable parts to be pushed out of the uninspected buffer to the first, second, third, and fourth buffers, a raw operation plan possibly specifying a non-integral quantity of unserviceable parts to be pushed out of the uninspected buffer to one or more of the first, second, third, and fourth buffers based on application of the first, second, third, and fourth rates, respectively, to an estimated quantity of unserviceable parts within the uninspected buffer; applying rounding logic to the quantities of unserviceable parts to be pushed out of the uninspected buffer to the first, second, third, and fourth buffers according to the one or more raw operation plans; and according to application of the rounding logic, generating one or more final operation plans for the inspection operation specifying only integral quantities of unserviceable parts to be pushed out of the uninspected buffer to the first, second, third, and fourth buffers.
 51. The software of claim 39, wherein the operation plan for each sourcing operation reflects a move order for initiating shipment of one or more unserviceable parts from the repair location to the associated upstream repair location.
 52. The software of claim 51, wherein the move order specifies a reverse Bill of Distribution (BOD).
 53. The software of claim 39, wherein the move lead time for each sourcing operation comprises one or more full days.
 54. The software of claim 39, wherein generating an operation plan for each of one or more sourcing operations comprises: traversing the repair locations in the repair network level by level, starting with one or more repair locations within a most downstream level and traversing upstream; for each repair location, for each future time for which a buffer profile of the second buffer indicates an inventory increase: estimating a quantity of unserviceable parts that can be pushed out of the second buffer to each of one or more upstream repair locations without leaving an insufficient quantity of unserviceable parts in the second buffer for a move operation already approved for a specified quantity of unserviceable parts at a specified future time to occur; and generating an operation for each sourcing operation according to the estimated quantity to consume unserviceable parts from the second buffer and produce unserviceable parts into one or more destination buffers at the associated upstream repair location; and for each time for which the buffer profile of the second buffer indicates an inventory decrease as a result of a move operation already approved for a specified quantity of unserviceable parts at a specified future time, generating an operation plan for each sourcing operation to produce unserviceable parts into one or more destination buffers at the associated upstream repair location.
 55. The software of claim 39, wherein generating an operation plan for each of one or more sourcing operations comprises: generating a raw operation plan for each sourcing operation, the raw operation plan possibly specifying a non-integral quantity of unserviceable parts to be pushed out of the second buffer to the associated upstream repair location; applying rounding logic to the quantities of unserviceable parts to be pushed out of the second buffer according to the raw operation plans; and according to application of the rounding logic, generating a final operation plan for each sourcing operation specifying an integral quantity of unserviceable parts to be pushed out of the second buffer to the associated upstream repair location.
 56. The software of claim 39, wherein the one or more components are collectively operable to: model for the repair location: an unserviceable parts buffer for unserviceable parts encompassing the uninspected buffer, the first buffer, and the second buffer; and a serviceable parts buffer for serviceable parts encompassing the fourth buffer and a good parts buffer for serviceable parts available to be put to service to help satisfy a demand; and track time-varying inventories of unserviceable parts in the unserviceable parts buffer and serviceable parts in the serviceable parts buffer, the unserviceable parts inventory being tracked separately from the serviceable parts inventory.
 57. The software of claim 39, comprising a replenishment planning engine of a service parts planning system.
 58. A system for repair planning comprising multiple components collectively operable to: for each of a plurality of repair locations in a multi-level repair network, each level comprising one or more repair locations at which unserviceable parts may be repaired, model: an uninspected buffer for unserviceable parts received at the repair location but not yet inspected at the repair location; a first buffer for unserviceable parts inspected at the repair location and determined to be repairable at the repair location, the unserviceable parts within the uninspected buffer being assigned to the first buffer at a first rate according to a first inspection sub-operation at the repair location; a second buffer for unserviceable parts inspected at the repair location and determined not to be repairable at the repair location, the unserviceable parts within the uninspected buffer being assigned to the second buffer at a second rate according to a second inspection sub-operation at the repair location; a third buffer for unserviceable parts inspected at the repair location and determined not to be repairable at any repair location in the repair network, the unserviceable parts within the uninspected buffer being assigned to the third buffer at a third rate according to a third inspection sub-operation at the repair location; a fourth buffer for unserviceable parts inspected at the repair location and determined to be serviceable without repair, the unserviceable parts within the uninspected buffer being assigned to the fourth buffer at a fourth rate according to a fourth inspection sub-operation at the repair location; an unserviceable parts buffer for unserviceable parts encompassing the uninspected buffer, the first buffer, and the second buffer; and a serviceable parts buffer for serviceable parts encompassing the fourth buffer and a good parts buffer for serviceable parts available to be put to service to help satisfy a demand; for each of the plurality of repair locations, generate operation plans for the inspection sub-operations to push unserviceable parts out of the uninspected buffer to the first, second, third, and fourth buffers according to the first, second, third, and fourth rates, respectively, each inspection sub-operation having a predetermined disposition time, an unserviceable part that is pushed out of the uninspected buffer being available within the first, second, third, or fourth buffer only after the predetermined disposition time for the associated inspection sub-operation has elapsed; for each of the plurality of repair locations, generate an operation plan for each of one or more sourcing operations to push unserviceable parts out of the second buffer to one or more upstream repair locations, each upstream repair location being associated with a sourcing operation having a predetermined move lead time, an unserviceable part that is pushed out of the second buffer being available at an upstream repair location only after the predetermined move lead time for the associated sourcing operation has elapsed; for a particular repair location, for each unserviceable part pushed out of the uninspected buffer to the first or second buffer, estimate the earliest time at which a repair operation can begin for the unserviceable part at the particular repair location or an upstream repair location, this earliest repair time determining the earliest time at which, after the unserviceable part has been repaired to make it serviceable, the serviceable part can be available to satisfy a demand at the particular repair location; perform the modeling, generating, generating, and estimating being performed for each of a plurality of times within a planning horizon; and for each of a plurality of repair locations, track time-varying inventories of unserviceable parts in the unserviceable parts buffer and serviceable parts in the serviceable parts buffer, the unserviceable parts inventory being tracked separately from the serviceable parts inventory. 